Investment securities - Investment Securities Realized Gains and Losses (Detail) - USD ($) $ in Thousands |
3 Months Ended | 6 Months Ended | ||
|---|---|---|---|---|
Jun. 30, 2026 |
Jun. 30, 2025 |
Jun. 30, 2026 |
Jun. 30, 2025 |
|
| Investments, Debt and Equity Securities [Abstract] | ||||
| Gross realized gains | $ 0 | $ 0 | $ 6,000 | $ 0 |
| Gross realized losses | 0 | 0 | (2,000) | 0 |
| Net realized gains | $ 0 | $ 0 | $ 4,000 | $ 0 |